Counter rotating facegear gearbox

ABSTRACT

A gearbox assembly includes a first face gear driveable about a face gear axis in a first direction by at least one first pinion gear and a second face gear driveable about the face gear axis in a second direction opposite the first direction by at least one second pinion gear. A thrust bearing is located between the first face gear and the second face gear. The first face gear is configured to drive rotation of a first shaft in the first direction and the second face gear is configured to drive rotation of a second shaft in the second direction. Further disclosed is a power train for a rotary wing aircraft having a gearbox including a first face gear rotatable in a first direction and a second face gear rotatable in a second direction opposite the first direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/022,405 filed on Feb. 7, 2011 and further claims priority to provisional application 61/301,866 filed on Feb. 5, 2010, the contents of which are incorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to drive trains. More specifically, the subject disclosure relates to gearboxes for rotary-wing aircraft.

Rotary-wing aircraft require a gearbox to transfer power from the engine or engines to the rotary wing. Since the desired rotational velocity of the rotor is lower than that of the engine, the rotational velocity transferred from the engine to the rotor must be reduced in the gearbox via a gear reduction system. The velocity reduction is accomplished via one or more intermediate gears between the engine and an output gear which drives the rotor. The rotational velocity reduction via these intermediate gears also increases a torque transferred to the output gear, so that the output gear size must be increased to withstand the torque applied. In some rotary-wing aircraft, especially ones with two counter-rotating rotors, the resulting gearbox is large and heavy. For example, some gearboxes for such aircraft have two separate output bull gears, driven by a pair of pinions connected to the bull gears by a spiral bevel mesh. The two bull gears and ancillary components take up considerable space and result in a heavy gearbox. Since both space and weight are at a premium in any aircraft, the art would favorably receive a rotary ring aircraft gearbox which has improvements in size and weight.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a gearbox assembly includes a first face gear driveable about a face gear axis in a first direction by at least one first pinion gear and a second face gear driveable about the face gear axis in a second direction opposite the first direction by at least one second pinion gear. A thrust bearing is located between the first face gear and the second face gear. The first face gear is configured to drive rotation of a first shaft in the first direction and the second face gear is configured to drive rotation of a second shaft in the second direction.

According to another aspect of the invention, a gearbox for a rotary wing aircraft includes a first face gear driveable about a face gear axis in a first direction by at least one first pinion gear and a second face gear driveable about the face gear axis in a second direction opposite the first direction by at least one second pinion gear. A thrust bearing is located between the first face gear and the second face gear. The first face gear is configured to drive rotation of a first rotor in the first direction and the second face gear is configured to drive rotation of a second rotor in the second direction.

According to yet another aspect of the invention, a powertrain for a rotary wing aircraft includes at least one engine having an engine shaft. The powertrain further includes a gearbox having a first face gear operably connected to the engine shaft driveable about a face gear axis in a first direction by at least one first pinion gear and a second face gear operably connected to the engine shaft driveable about the face gear axis in a second direction opposite the first direction by at least one second pinion gear. A thrust bearing is located between the first face gear and the second face gear. A first rotor is connected to the first face gear and thereby rotatable in the first direction and a second rotor is connected to the second face gear and thereby rotatable in the second direction.

These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic view of an embodiment of a rotary wing aircraft;

FIG. 2 is a partial schematic view of an embodiment of a gearbox;

FIG. 3 is another partial schematic of an embodiment of a gearbox;

FIG. 4 is a cross-sectional view of an embodiment of a gearbox; and

FIG. 5 is a partial schematic of another embodiment of a gearbox.

The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Shown in FIG. 1 is a cross-sectional view of a rotary wing aircraft 10. The aircraft 10 includes an upper rotor 12 and a lower rotor 14, which in some embodiments is configured to rotate in a direction opposite to the rotation of the upper rotor 12 about a rotor axis 18. The upper rotor 12 and lower rotor 14 are driven by an upper rotor shaft 20 and lower rotor shaft 22 (shown in FIG. 4). One or more engines 24 supply power to the upper rotor shaft 20 and lower rotor shaft 22 via a gearbox 26. The gearbox 26 is configured to transfer rotation of an engine shaft 28 into rotation of the upper rotor shaft 20 and lower rotor shaft 22 and to also provide speed reduction from a rotational speed of the engine shaft 28 to a desired rotation speed of the upper rotor shaft 20 and lower rotor shaft 22.

Referring now to FIG. 2, shown is a schematic view of an embodiment of a gearbox 26. The gearbox 26 is connected to the engine 24 via the engine shaft 28. The engine shaft 28 includes an engine shaft gear 30 disposed at one end to drive two first reduction gears 32 which, in some embodiments, are disposed at opposing sides of the engine shaft gear 30. Engine shaft gear teeth 34 disposed at an outer periphery 36 of the engine shaft gear 30 mesh with first reduction gear teeth 38 thus splitting a torque transmitted through the engine shaft 28. Further, the first reduction gears 32 have a larger diameter than the engine shaft gear 30 to reduce a rotational speed of the system. In some embodiments, the engine shaft gear 30 and/or the first reduction gears 32 are beveled to enable improved meshing therebetween.

Each first reduction gear 32 includes a first reduction output gear 40 which transfers rotational energy of the first reduction gear 32 to one or more second reduction gears 42 via a plurality of first reduction output teeth 44. The output gear 40 is connected the first reduction gear 32 via a torsionally compliant member 48, such as a torsional spring, which allows for some absorption of torque between the output gear 40 and the first reduction gear 32. The plurality of first reduction output teeth 44 mesh with a plurality of second reduction gear teeth 46 to drive rotation of the one or more second reduction gears 42. In the embodiment shown in FIG. 2, each first reduction output gear 40 drives two second reduction gears 42, an upper second reduction gear 42 a and a lower second reduction gear 42 b.

Referring now to FIG. 3, each second reduction gear 42 includes a pinion shaft 68 extending axially therefrom. A pinion gear 50 is secured to each pinion shaft 68 such that rotation of the second reduction gear 42 rotates the pinion gear 50. Each pinion gear 50 rotates in the same direction as its associated second reduction gear 42, upper pinion gear 50 a associated with upper second reduction gear 42 a and lower pinion gear 50 b associated with lower second reduction gear 42 b. Each pinion gear 50 meshes with a face gear 52 of a face gear assembly 54. The face gear assembly 54 includes two face gears 52 stacked along face gear axis 56 with a thrust bearing 58 disposed between a first face gear 52 a and a second face gear 52 b. In some embodiments, the first face gear 52 a and the second face gear 52 b are coaxial. The upper pinion gears 50 a mesh with a first side 60 of the first face gear 52 a to drive the first face gear 52 a in a first direction 62 about the face gear axis 56. Similarly, the lower pinion gears 50 b mesh with a second side 64 of the second face gear 52 b to drive the second face gear 52 b in a second direction 66 about the face gear axis 56, where the first direction 62 is opposite the second direction 66.

The placement of the thrust bearing 58 between the first face gear 52 a and the second face gear 52 b permits the counter-rotation of the first face gear 52 a and the second face gear 52 b. The thrust bearing 58 extends circumferentially between the first face gear 52 a and second face gear 52 b and may comprise ball elements, cylindrical elements, air, and/or film lubricant or other suitable bearing elements to allow the counter-rotation. In some embodiments, as illustrated in FIG. 4, the face gear assembly 54 is preloaded to retain the thrust bearing 58 in a desired location. Essentially, the first face gear 52 a and the second face gear 52 b are urged toward each other to retain the thrust bearing 58 in a bearing cavity 68 between the first face gear 52 a and the second face gear 52 b.

Referring again to FIG. 3, multiple pinion gears 50 may be utilized to drive each of the face gears 52. The embodiment of FIG. 3 utilizes two pinion gears 50 to drive each face gear 52, but other quantities of pinion gears 50 may be utilized. Using multiple pinion gears 50 provides redundancy in the event of problems with or failure of a pinion gear 50, and also through torque splitting reduces a torque applied by each pinion gear 50 thus reducing stresses in the gearbox 26. It is to be appreciated, however, that if such redundancy is not necessary or desired, a single pinion gear 50 may be utilized to drive rotation of each face gear 52.

As shown in FIG. 4, the upper rotor shaft 20 is connected to the second face gear 52 b via, for example, a spline connection 70 such that rotation of the second face gear 52 b drives rotation of the upper rotor shaft 20. Similarly, the lower rotor shaft 22 is secured to the first face gear 52 a such that rotation of the first face gear 52 a drives rotation of the lower rotor shaft 22. Since the face gears 52 a and 52 b are rotating in opposite directions, the upper rotor shaft 20 and lower rotor shaft 22 will likewise rotate in opposite directions.

Referring now to FIG. 5, in some embodiments one or more power take-offs 72 are located at the face gear assembly 54. The power take offs 72 may be to provide power to a tail rotor or other accessories. In some embodiments, the power take offs 72 are located circumferentially at locations around the face gear assembly 54 to prevent distortion or rippling of the face gear assembly 54.

The embodiments of the gearbox 26 shown in the FIGs utilize rotational energy from one engine 24. It is to be appreciated, however, that the gearbox 26 may be adapted to utilize power from multiple engines 24 through, for example, the provision of more than one engine shaft 28. Further, two levels of torque split and gear reduction are provided by the first reduction gears 32 and second reduction gears 40. If additional torque splitting and/or gear reduction is necessary, more reduction gears, for example, third and/or fourth reduction gears, may be utilized.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims. 

The invention claimed is:
 1. A method of operating a gearbox comprising: rotating a first face gear about a face gear axis in a first direction; positioning a thrust bearing for direct contact between the first face gear and a second face gear located at the face gear axis; rotating the second face gear about the face gear axis in a second direction opposite the first direction; driving rotation of a first shaft in the first direction via the rotation of the first face gear; and driving rotation of a second shaft in the second direction via the rotation of the second face gear.
 2. The method of claim 1 further comprising: driving the first face gear about the face gear axis via at least one first pinion gear; and driving the second face gear about the face gear axis via at least one second pinion gear.
 3. The method of claim 2, further comprising driving the at least one first pinion and the at least one second pinion via at least one first reduction gear.
 4. The method of claim 1, further comprising urging the first face gear toward the second face gear along the face gear axis to retain the thrust bearing therebetween.
 5. The method of claim 1, wherein the thrust bearing comprises ball elements, cylindrical elements, air, film lubricant or combinations thereof.
 6. A rotary-winged aircraft comprising: an airframe; a powertrain disposed at least partially at the airframe including: at least one engine having an engine shaft; and a gearbox including: a first face gear operably connected to the engine shaft driveable about a face gear axis in a first direction; a second face gear operably connected to the engine shaft driveable about the face gear axis in a second direction opposite the first direction; and a thrust bearing disposed for direct contact between the first face gear and the second face gear; a first rotor connected to the first face gear and thereby rotatable in the first direction; and a second rotor connected to the second face gear and thereby rotatable in the second direction.
 7. The aircraft of claim 6, further comprising: at least one first pinion gear to drive the first face gear about the face gear axis; and at least one second pinion gear to drive the second face gear about the face gear axis.
 8. The aircraft of claim 7, wherein the at least one first pinion gear and the at least one second pinion gear are operably connected to and driven by at least one first reduction gear.
 9. The aircraft of claim 8 wherein the at least one first reduction gear is operably connected to at least one input shaft.
 10. The aircraft of claim 8 wherein the at least one first pinion gear and the at least one second pinion gear are each operably connected to the at least one first reduction gear via a second reduction gear.
 11. The aircraft of claim 6 wherein the first face gear includes a spline to connect the first face gear to the first rotor.
 12. The aircraft of claim 6 wherein the second face gear includes a spline to connect the second face gear to the second rotor.
 13. The aircraft of claim 6, wherein the first face gear is preloaded toward the second face gear along the face gear axis to retain the thrust bearing therebetween.
 14. The aircraft of claim 6, wherein the thrust bearing comprises ball elements, cylindrical elements, air, film lubricant or combinations thereof. 